The shipping industry is becoming increasingly visible on the global environmental agenda as air emissions from vessels make an increasingly conspicuous contribution to air quality. With the forecast expansion of world trade; scientists are estimating global emissions to increase by 30% to 1.45 billion tonnes in the next decade. This would make shipping responsible for 6% of global emissions by 2020. The International Marine Organisation (IMO) Annex VI entered into force in 2005 and is currently the most important international treaty governing emissions to air from ocean going vessels. It has set strict limits on sulphur dioxide (SO2) and nitrogen oxide (NOx) emissions from ship exhausts, prohibits the deliberate emissions of ozone depleting substances, and places a global cap on the sulphur content of marine fiiel. As an alternative to using low sulphur fliel oils, ships have the option to fit an exhaust gas cleaning system such as a seawater scrubber (SWS) or to use any other feasible technology to limit SO2 emissions. SWS transfers SOx (ca. 95%) and partly NOx (ca. 20%) into aqueous solution, producing acidic solutions which are then buffered with seawater and finally discharged into the sea.